• Title, Summary, Keyword: analytical substructure

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Development of Analysis Program for Mega Frame System (메가골조구조물 전용 해석프로그램의 개발)

  • Kim Hyun-Su;Yu Il-Hyang;Lee Dong-Guen
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.873-880
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    • 2006
  • Since the mega frame structure has significant numbers of elements and nodes, it takes tremendous times and computer memories to analyze and design the structures. Therefore, the exclusive structural analysis program for mega frame system is developed to reduce the efforts and time required for the analysis and design of mega frame structure. To this end, an efficient modelling technique using the characteristics of mega frame structures and an efficient analytical model, which uses a few DOFs selected by the user using the matrix condensation method. are developed in tins study. Static and dynamic analyses are conducted using an example structure.

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Effects of Blade Shape on the Dynamics of Turbo-machinery (깃 형상이 터보기계의 동특성에 미치는 영향)

  • 전상복
    • Journal of KSNVE
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    • v.8 no.3
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    • pp.477-484
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    • 1998
  • An analytical procedure on the base of the substructure synthesis and assumed modes method is developed to investigate the flexibility effect of bladed disk assembly on vibrational modes of flexible rotor system. In modeling the system, Coriolis forces, gyroscopic moments, and centrifugal stiffening effects are taken into account. The coupled vibrations between the shaft and bladed disk are then extensively investigated through the numerical simulation of simplified models, with varying the shaft rotational speed and the prewist and stagger angles of the blade. It is found that the Coriolis and inertia forces and the inertia torque, which are induced by the one nodal diameter modes of the bladed disk and vary depending upon the stagger and prewist angles, lead to the coupled motions of the shaft and the bladed disk.

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Structural Dynamic Analysis using Multi-FRF Synthesis Method (다중전달 함수합성법을 이용한 구조물의 동특성 해석)

  • 정재훈;지태한;박영필
    • Journal of KSNVE
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    • v.8 no.1
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    • pp.139-145
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    • 1998
  • A great deal of effort has been invested in upgrading the performance and the efficiency of dynamic analysis of mechanical structures. Using experimental modal analysis(EMA) or finite element analysis(FEA) data of mechanical structures, the performance and efficiency can be effectively evaluated. In order to analyze complex structures such as automobiles and aircrafts, for the sake of computing efficiency, the dynamic substructuring techniques that allow to predict the dynamic behavior of a structure are widely used. Through linking a modal model obtained from EMA and an analytical model obtained from FEA, the best conditioned strucutres can be proposed. In this study, a new algorithm of substructre synthesis method, Multi-FRF synthesis method, is proposed to analyze a structure composed of many substructures.

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Dynamic Analysis of Harmonically Excited Non-Linear Structure System Using Harmonic Balance Method

  • Mun, Byeong-Yeong;Gang, Beom-Su;Kim, Byeong-Su
    • Journal of Mechanical Science and Technology
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    • v.15 no.11
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    • pp.1507-1516
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    • 2001
  • An analytical method is presented for evaluation of the steady state periodic behavior of nonlinear structural systems. This method is based on the substructure synthesis formulation and a harmonic balance procedure, which is applied to the analysis of nonlinear responses. A complex nonlinear system is divided into substructures, of which equations are approximately transformed to modal coordinates including nonlinear term under the reasonable procedure. Then, the equations are synthesized into the overall system and the nonlinear solution for the system is obtained. Based on the harmonic balance method, the proposed procedure reduces the size of large degrees-of-freedom problem in the solving nonlinear equations. Feasibility and advantages of the proposed method are illustrated using the study of the nonlinear rotating machine system as a large mechanical structure system. Results obtained are reported to be an efficient approach with respect to nonlinear response prediction when compared with other conventional methods.

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Lateral deformation capacity and stability of layer-bonded scrap tire rubber pad isolators under combined compressive and shear loading

  • Mishra, Huma Kanta;Igarashi, Akira
    • Structural Engineering and Mechanics
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    • v.48 no.4
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    • pp.479-500
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    • 2013
  • This paper presents the experimental as well as analytical study conducted on layer-bonded scrap tire rubber pad (STRP) isolators to develop low-cost seismic isolators applicable to structures in developing countries. The STRP specimen samples were produced by stacking the STRP layers one on top of another with the application of adhesive. In unbonded application, the STRP bearings were placed between the substructure and superstructure without fastening between the contact surfaces which allows roll-off of the contact supports. The vertical compression and horizontal shear tests were conducted with varying axial loads. These results were used to compute the different mechanical properties of the STRP isolators including vertical stiffness, horizontal effective stiffness, average horizontal stiffness and effective damping ratios. The load-displacement relationships of STRP isolators obtained by experimental and finite element analysis results were found to be in close agreement. The tested STRP samples show energy dissipation capacity considerably greater than the natural rubber bearings. The layer-bonded STRP isolators serve positive incremental force resisting capacity up to the shear strain level of 150%.

Interaction fields based on incompatibility tensor in field theory of plasticity-Part II: Application-

  • Hasebe, Tadashi
    • Interaction and multiscale mechanics
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    • v.2 no.1
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    • pp.15-30
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    • 2009
  • The theoretical framework of the interaction fields for multiple scales based on field theory is applied to one-dimensional problem mimicking dislocation substructure sensitive intra-granular inhomogeneity evolution under fatigue of Cu-added steels. Three distinct scale levels corresponding respectively to the orders of (A)dislocation substructures, (B)grain size and (C)grain aggregates are set-up based on FE-RKPM (reproducing kernel particle method) based interpolated strain distribution to obtain the incompatibility term in the interaction field. Comparisons between analytical conditions with and without the interaction, and that among different cell size in the scale A are simulated. The effect of interaction field on the B-scale field evolution is extensively examined. Finer and larger fluctuation is demonstrated to be obtained by taking account of the field interactions. Finer cell size exhibits larger field fluctuation whereas the coarse cell size yields negligible interaction effects.

A Study on the estimation of an equivalent system of a local vibration system of a huge structure and the Optimum Structural Modification Method (거대 구조물의 국부진동계의 등가계 산출과 이를 이용한 최적구조변경법)

  • 박석주;황문주;오창근;김성우
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • pp.120-127
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    • 1998
  • It is very difficult to execute the vibration analysis of a huge strucutre, which takes up much time and expense. In this paper we intend to make the equivalent system of a local vibration system of a huge structure with a view to improving the dynamic characteristics and reducing time and expense. First of all, upper deck structure model is maded. And we perform the vibration analysis by the Substructure Synthesis Method and execute the exciting test for the upper deck structure model, and observe the coincidences of two results to confirm the reliability of the analyzing tools used. To make the equivalent system, we give boundary condition to sub-structure that want to be modified and execute the Sensitivity Analysis Method and the Optimum Structural Modification Method. And we execute the structural modification of the equivalent system.. The following can be found from this study. 1. The analytical results are generally coincident with each other. 2. The equivalent system of the superstructure model can be easily obtained using the sensitivity analysis metho and the optimum structural modification method. 3. The structural modification using the equivalent system can be obtained good results above 90% of object value.

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Normalized Subgrade Analytical Model Considering Stress-Dependency and Modulus Degradation (응력의존성 및 탄성계수 감쇠특성을 고려한 노상토의 정규화 해석모델)

  • Kim, Ji-Hwan;Kang, Beong-Joon;Lee, Jun-Hwan;Kweon, Gi-Chul
    • Journal of the Korean Geotechnical Society
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    • v.24 no.4
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    • pp.37-46
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    • 2008
  • Application of resilient modulus, representing mechanical behavior of pavement materials, has become general concept for pavement design, analysis and maintenance after '86 AASHTO selected it as a basic input property of subgrade. It is known that resilient modulus of domestic subgrade soil is affected greatly by material factors, such as water content and dry weight unit, and stress components, such as deviatoric stress and confining stress, while effects of loading frequency and loading repeat were regarded negligible. If design based on resilient modulus is to be successfully implemented, design input variables of relevant models should be able to reflect local conditions. In this study, generalized mechanical model for subgrade is proposed. Model parameters are estimated from test results. Verification of the model was performed through finite element analysis using the proposed model, which showed good agreement with measured results of pavement deflections.

Design Requirements Review and Time-dependant CP Performance Analysis for Corrosion Protection Design Optimization of Offshore Structure (해상구조물의 방식설계 최적화를 위한 설계요건 분석 및 시간의존적 방식성능 해석)

  • Park, Jae-Cheul;Choi, Yoo-Youl;Pyeon, Kang-Il;Chun, Kang-Woo;Jang, Hwa-Sup;Roh, Gill-Tae
    • Journal of the Korean institute of surface engineering
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    • v.49 no.5
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    • pp.408-415
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    • 2016
  • The offshore structures exposed to harsh corrosive such as the marine environment is essential for the quality management technique throughout the life cycle of initial design, construction and operation. Also, it should satisfy the design life and ensure the safety of the substructure with optimization of design process. This study focused on optimization of design condition for corrosion protection of wind turbine structure and computational analyzing was performed to evaluate the performance of corrosion protection with utilizing practical experimental data. We expect this analytical study contribute to improve the corrosion maintenance stability and economical efficiency of designing wind turbine structures. As a result, the design of cathodic protection system using sacrificial anodes required accurate identification of current density in order to meet the long term design life, which can be seen that a change of structure surface's coating breakdown factor is one of the key influencing factors.

Real-time hybrid testing using model-based delay compensation

  • Carrion, Juan E.;Spencer, B.F. Jr.
    • Smart Structures and Systems
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    • v.4 no.6
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    • pp.809-828
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    • 2008
  • Real-time hybrid testing is an attractive method to evaluate the response of structures under earthquake loads. The method is a variation of the pseudodynamic testing technique in which the experiment is executed in real time, thus allowing investigation of structural systems with time-dependent components. Real-time hybrid testing is challenging because it requires performance of all calculations, application of displacements, and acquisition of measured forces, within a very small increment of time. Furthermore, unless appropriate compensation for time delays and actuator time lag is implemented, stability problems are likely to occur during the experiment. This paper presents an approach for real-time hybrid testing in which time delay/lag compensation is implemented using model-based response prediction. The efficacy of the proposed strategy is verified by conducting substructure real-time hybrid testing of a steel frame under earthquake loads. For the initial set of experiments, a specimen with linear-elastic behavior is used. Experimental results agree well with the analytical solution and show that the proposed approach and testing system are capable of achieving a time-scale expansion factor of one (i.e., real time). Additionally, the proposed method allows accurate testing of structures with larger frequencies than when using conventional time delay compensation methods, thus extending the capabilities of the real-time hybrid testing technique. The method is then used to test a structure with a rate-dependent energy dissipation device, a magnetorheological damper. Results show good agreement with the predicted responses, demonstrating the effectiveness of the method to test rate-dependent components.